This invention relates in general to devices for testing the contents of a person's breath to determine the presence of alcohol, and in particular to a new and useful device and method for effecting the testing of the expiration air for alcohol.
Breathing alcohol testing devices must be carried along by the user and must be ready for use. The measuring result should be sufficiently accurate, despite the frequently adverse circumstances under which the measurements must be made in the open air. The lack of cooperation of the test person must not affect the measuring unit.
In a known breathing alcohol testing device, the test person blows directly into a testing tube through a mouthpiece. The amount of expiration gas which is necessary to determine the alcohol concentration in the expiration air, is found by means of a measuring bag arranged behind the testing tube, which must be inflated. This known method requires tubes with a low resistance in order to keep the blowing effort of the test person within limits. The breathing alcohol testing tubes must therefore have a relatively large cross section and may only have a short preparation layer. Since the length of the discoloration of the preparation is a measure of the alcohol content in the expiration air, an extension would mean a greater measuring sensitivity (German Pat. No. 10 52 630).
A known device for measuring the expiration gas mixture by means of a breathing alcohol testing tube has a breath sample chamber with a defined maximum volume. It is brought by the breath from a starting position into an end position, so that it contains a breath sample of a defined volume. When the breath sample chamber is full, a pump goes into action with which the breathing air contained in the breath sample chamber is fed over a line to and through the breathing alcohol testing tube. The guidance of the breathing air over the breath sample chamber leads to difficulties, caused by cooling. In order to avoid this, the entire device, not only the chamber, but all lines are heated. The device is therefore complicated, voluminous, and requires principally a heating period before use (German Pat. No. 12 98 311).